How to stop Firefox from automatically making connections without my permission

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Some people are particularly concerned about the connections Firefox makes to the Internet, especially when such connections are made with no apparent cause. This article will explain the various reasons why Firefox may make a connection to the Internet, and how you can stop it from doing so if you so desire.

Loopback connection

A loopback connection (to IP address 127.0.0.1) can be made by Firefox on non-Unix machines. In this case the browser is communicating with itself as expected, and it is not recommended that this communication be blocked. See bug 100154 for more information.

Live Bookmarks updating

Live Bookmarks automatically reload themselves on a regular basis, and in doing so will make a connection to the Internet. Deleting all your Live Bookmarks will stop these connections from being made.

Auto-update checking

Warning: Disabling update checking is not recommended and will leave you open to security vulnerabilities that get fixed in newer versions.

Firefox occasionally checks to see if any updates are available for itself and for your search engines. To disable these checks:

At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.

Firefox also checks to see if any updates are available for your add-ons (extensions, themes). To disable this check:

At the top of the Firefox window, click on the Firefox buttonOn the menu bar, click on the Tools menuAt the top of the Firefox window, click on the Tools menu, and then click Add-ons. The Add-ons Manager tab will open.Click the menu button
and choose Add-ons. The Add-ons Manager tab will open.

In the Add-ons Manager tab, select the Extensions panel.

At the top of the tab, click the Tools for All Add-ons menu and uncheck Update Add-ons Automatically, then select Reset All Add-ons to Update Automatically.

Home page loading

Your home page may be loading. To change your home page to something that doesn't generate connections to the Internet:

At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.

Click the menu button
and choose Options.Preferences.

Select the General panel.

Either set When Firefox starts to Show a blank page or set it to Show my home page and click Restore to Default.

Anti-phishing list updating

Warning: Disabling the anti-phishing protection is not recommended, as it will leave you vulnerable to untrustworthy websites that might try to steal your financial information and/or your identity.

At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.

Click the menu button
and choose Options.Preferences.

Select the Security panel.

Uncheck Block reported web forgeries.

Anti-malware list updating

Warning: Disabling the anti-malware protection is not recommended, as it will leave you vulnerable to malicious file downloads or untrustworthy websites that might try to infect you with a virus, trojan or spyware.

At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then select Options.On the menu bar, click on the Firefox menu and select Preferences....At the top of the Firefox window, click on the Edit menu and select Preferences.

Click the menu button
and choose Options.Preferences.

Select the Security panel.

Uncheck Block reported attack sites.

Add-on list prefetching

Each time the Add-ons manager is opened, Firefox prefetches a list of add-ons to improve responsiveness of the Get Add-ons pane. This connection is not made if the add-ons manager is not opened.

Blocklist updating

Warning: Disabling the blocklist is not recommended, as it may result in you using untrustworthy add-ons or graphics drivers that can cause Firefox to crash.

The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.

In the about:config page, search for the preference extensions.blocklist.enabled.

Observe the Value column of the extensions.blocklist.enabled row.

If it is set to false then do nothing.

If it is set to true, double-click on it to set it to false.

Add-on metadata updating

The Add-ons manager displays information about each add-on you have installed and provides personalized recommendations in the Get Add-ons pane. To keep this data updated, Firefox will request information from the Mozilla Add-ons gallery once a day (for more information, see this blog post). To disable these updates:

The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.

In the about:config page, search for the preference network.prefetch-next.

Observe the Value column of the network.prefetch-next row.

If it is set to false then do nothing.

If it is set to true, double-click on it to set it to false.

New Tab Page

To improve the loading speed of commonly visited websites, Firefox will open connections to sites when the user hovers their mouse over thumbnails on the New Tab Page. In the event that the user clicks on the thumbnail, the site can begin loading faster since some of the work was already started in advance. Currently, there is not a way to disable this kind of prefetching, but you can always turn off New Tab Page thumbnails.

Extensions

An extension you have installed may be making a connection to a website that it relies on. For example, a connection to a website to synchronize your bookmarks, a connection to a website to update a list of sites to block, etc. Or it is possible an extension could be changing the expected behavior of Firefox in other ways. For example, FasterFox extension has an option to prefetch all links.

Infected with malware

If your computer is infected with a virus, trojan, spyware, or other malicious software, then Firefox's Internet connection may be being piggybacked in order for the malware to communicate with its author or to deliver advertisements, etc. (for more information, see Troubleshoot Firefox issues caused by malware). If you suspect this is the case, consider seeking advice from one of these forums specializing in malware removal: